Tool for electrochemical contouring of workpieces



y 1968 HANS-DIETER TRENN ETAL 3,393,141

TOOL FOR ELECTROCHEMICAL CONTOURING OF WORKPIECES Filed May 11, 1965Fig.4 Fig.5

Fig.6 Fig.7

United States Patent 3,393,141 TOOL FOR ELECTROCHEMICAL CONTOURING 0FWORKPIECES Hans-Dieter Trenn and Gerhard Hebold, Mulheim (Ruhr),Germany, assignors to Siemens Aktiengesellschaft, Munich, Germany, acorporation of Germany Filed May 11, 1965, Ser. No. 454,949 Claimspriority, application Germany, May 16, 1964,

8 Claims. (Cl. 204-224) Our invention relates to the production ofcontours or profiles on workpieces by electrochemical processing. Suchcontouring work is performed by electrolysis with the aid of a templateelectrode which is shaped in accordance with the desired contour and ismoved relative to the workpiece to be shaped.

Electrochemical contouring with such electrolytical template tools,however, becomes difiicult or deficient in cases where precise cornersor edges at the workpiece are required. These difiiculties are mainlydue to the fact that the corresponding corners of the template contourcause irregularities in the flow of electrolyte so that sludge tends toaccumulate in such corners. This interferes with the chemical processingor may cause short circuits and leads to undesired changes in the shapeat the corners of the workpiece, so that these corners are no longersharp but more or less rounded.

It is an object of our invention to improve electrochemical templatetools so as to avoid or minimize such difiiculties and trouble. Another,more specific object of the invention is to devise an electrochemicaltemplate of a cornered contour shape that reliably secures a troublefreedrainage of the sludge-containing electrolyte at the corners of thetool.

According to the invention, we provide the template tool electrode atthe corners of the workpiece contour with respective recesses whichwiden the electrolyte flow path at each corner. Preferably, the recessesare located symmetrically to the respective bisectors of the cornerangles.

The recesses may be formed as slits. Their width may be dimensioned inaccordance with the particular working conditions of the tool, such asthe electric current intensity, voltage, rate of tool feed movement, 01:the particular workpiece material. With proper recess dimensions, anyburr formation or accumulation of material at the corners can be readilyprevented. Thus, the recess-forming slits in the tool reliably preventburr formation, if the slit width at each corner amounts to about twicethe width of the processing gap at the longitudinal faces of theworkpiece being processed.

The invention will be further described with reference to the drawing inwhich:

FIG. la illustrates schematically a known electrolytic contouringdevice, and FIG. 1b is a front view of the contouring electrode of thedevice.

FIG. 2 illustrates the cross section of a workpiece electrolyticallyproduced by means of an electrode according to FIG. 117.

FIG. 3 shows part of a tool electrode according to the invention forproducing sharp edges at electrolytically contoured workpieces.

FIGS. 4 to 7 show modified contour shapes of tool electrodes otherwisedesigned according to FIG. 3.

The contouring device schematically illustrated in FIG. 1a comprises asupport a with a holder or chuck b for fastening a workpiece c to becontoured by electrolytical processing. The contour to be produced isdetermined by an annular template electrode 2d which is fastened to atubular electrode holder e on a carrier f. The carrier is supported on aslider (not shown) which is displaceable on the machine frame structureby suitable feed means 3,393,141 Patented July 16, 1968 in a directiontoward the workpiece. The support a and the holder 3 are connected tothe positive and negative leads of a suitable source of electriccurrent. Electrolyte is supplied through inlet and outlet tubes g and hto flow through the inner space of the tubular holder e and between theelectrode d and the workpiece c. The electrolytic action, then occurringbetween the template electrode d and the workpiece c, dissolves materialfrom the workpiece 0 thus shaping its contour in accordance with thetemplate contour of the tool electrode.

According to the front view of the electrode tool 0! shown in FIG. 1b,the template contour is that of a regular hexagon, so that theworkpiece, after the tool electrode has longitudinally passed over theentire length of the workpiece, has assumed a corresponding hexagonalshape.

The electrolyte continuously supplied during simultaneous axialdisplacement of the tool electrode relative to the workpiece mayconsist, for example, of an aqueous solution of sodium chloride orsodium nitrate. As a rule, the template contour of the tool is given aslightly larger size than required of the workpiece. Despite the sharpcorners of the template contour in the electrode tool d according toFIG. 1b, the resulting contour of the workpiece, shown in FIG. 2, doesnot have sharp edges but is slightly rounded. As mentioned above, thisis due to the fact that the sludge-containing electrolyte can not asreadily flow through the gap at the contour corners as at the otherlocalities along the perimeter.

In contrast thereto, FIG. 3 shows on larger scale a template toolaccording to the invention. This tool is distinguished by the fact thatthe electrode body 1 is provided with recess in form of slits 3 at therespective corners 2a of the workpiece contour to be produced. The slits3 are symmetrical to the bisectors 4 of the angles at the corners of theworkpiece contour, and they are given a width equal to 2B, if B denotesthe processing gap left between the planar faces of the workpiece 2 andthe corresponding template faces of the tool electrode. The gaps providean enlarged flow space for electrolyte passing through the gap so thatany detrimental accumulation of sludge in the region of the corners isavoided. It will be readily apparent, that the electrode slits can beaccurately dimensioned, in accordance with the particular operatingconditions (current intensity, voltage, rate of feed) to obtain anydesired shape at the sharp corners of the workpiece and to avoid burr orbulge formation.

The electrode slits or recesses 3 in the corner regions of the workpiecemay be given various other shapes. Some such other shapes areexemplified in FIGS. 4 and 5. According to FIG. 5, the slits arecontiguous to the corners of the template contour and each slit extendsfrom the corner in the radial outward direction with parallel slit wallsbut has a widened cylindrical bore 3a at the outermost end.

In the embodiment of FIG. 5 the walls 3b of the slits extend from thetemplate contour outwardly at an angle in such a manner that theindividual slit widens with increasing distance from the workpiece, theradially outward end of the slit being closed by an arcuate wall portion30 of the template electrode.

The invention is not limited to the processing of pris matic workpieceshaving a cross section of hexagonal shape, but is applicable, inprinciple, with any other crosssectional shapes limited by planar,curvilinear, or com posite planar and curvilinear surface portions. Forexample, FIGS. 6 and 7 show template contours with examples of asuitable design and location of the slits in tool electrodes forworkpieces of the latter types. For such composite workpiece contours,the recesses or slits at the corner of the template contour arepreferably arranged in symmetrical relation to the bisector of the anglebetween the tangents of the curved wall portions forming the corner, orsymmetrically to the bisector of the angle between the tangent of acurved wall portion on the one hand and an adjacent planar wall portionon the other hand.

However, the invention is not limited to having the electrode slitsextend symmetrically to the abovementioned bisectors, and it issometimes also desirable to give the recesses or slits a width differentfrom the one memtioned in the above-described example.

We claim:

1. Device for electrochemical contouring of workpieces, comprising atool electrode having a template contour corresponding to a corneredworkpiece contour to be produced and adapted to form with the workpiecea perimetric gap to be traversed by electrolyte for removing materialfrom the workpiece, said electrode having respective recesses located atthe corners of the workpiece contour and forming in said electrode awidened flow path for electrolyte through the corner regions of thetemplate contour.

2. In an electrochemical contouring device according to claim 1, saidrecesses comprising respective slits extending outwardly from thetemplate contour.

3. In an electrochemical contouring device according to claim 2, each ofsaid slits extending substantially in symmetrical relation to thebisector of the angle at the corner of the workpiece contour.

4. In an electrochemical contouring device according to claim 2, saidslits adapted to have a width substantially twice as large as the widthof said gap.

5. In an electrochemical contouring device according to claim 2, saidslits having a shape widening from said template contour in the outwarddirection.

6. In an electrochemical contouring device according to claim 2, saidslits having a straight parallel-wall portion adjacent to said templatecontour and ending in the outward direction in a cylindrical portion oflarger width than said straight portion.

7. In an electrochemical contouring device according to claim 2, saidworkpiece contour having two curved faces meeting at one of saidcorners, and said slit ofsaid electrode at said one corner extending inSymmetrical relation to the bisector of the angle between the respectivetangents of said two curved faces.

8. In an electrochemical contouring device according to claim 2, saidworkpiece contour having a curved face and a planar face meeting at oneof said corners, and said slit of said electrode at said one cornerextending in symmetrical relation to the bisecto'r of the angle betweensaid planar face and the tangent of the curved face at said corner.

References Cited UNITED STATES PATENTS 3,288,699 11/1966 Trageretal. 204 22 1 3,324,021 6/1967 Haggerty 204 224 3,324,022 6/1967 Keeleric204224 JOHN H. MACK, Primary E ruminer.

D. VALENTINE, Assistant Examiner.

1. DEVICE FOR ELECTROCHEMICAL CONTOURING OF WORKPIECES, COMPRISING A TOOL ELECTRODE HAVING A TEMPLATE CONTOUR CORRESPONDING TO A CORNERED WORKPIECE CONTOUR TO BE PRODUCED AND ADAPTED TO FORM WITH THE WORKPIECE A PERIMETRIC GAP TO BE TRAVERSED BY ELECTROLYTE FOR REMOVING MATERIAL FROM THE WORKPIECE, SAID ELECTRODE HAVING RESPECTIVE RECESSES LOCATED AT THE CORNERS OF THE WORKPIECE CONTOUR AND FORMING IN SAID ELECTRODE A WIDENED FLOW PATH FOR ELECTROLYTE THROUGHT THE CORNER REGIONS OF THE TEMPLATE CONTOUR. 